Generally, the widely-used peripheral input device of a computer system includes for example a mouse device, a keyboard device, a trackball, or the like. Via the keyboard board, characters or symbols can be directly inputted into the computer system. As a consequence, most users and most manufacturers of input devices pay much attention to the development of keyboard devices.
Hereinafter, the structure of a conventional keyboard device will be illustrated with reference to FIG. 1. FIG. 1 is a schematic side cross-sectional view illustrating a conventional keyboard device. As shown in FIG. 1, the conventional keyboard device 1 comprises plural keycaps 11, plural scissors-type connecting elements 12, plural rubbery elastomers 13, a membrane switch circuit member 14 and a base 15. The plural keycaps 11, the plural scissors-type connecting elements 12, the plural rubbery elastomers 13 and the membrane switch circuit member 14 are supported by the base 15. The scissors-type connecting elements 12 are used for connecting the base 15 and the corresponding keycaps 11.
The membrane switch circuit member 14 comprises an upper wiring board 141, a spacer layer 142 and a lower wiring board 143. The upper wiring board 141 has plural upper contacts 1411. The spacer layer 142 comprises plural perforations 1421. The lower wiring board 143 comprises plural lower contacts 1431 corresponding to the plural upper contacts 1411. When a specified position of the membrane switch circuit member 14 is triggered, the upper contact 1411 corresponding to the triggered position is inserted into the corresponding perforation 1421 and contacted with the corresponding lower contact 1431. The upper contact 1411, the corresponding perforation 1421 and the corresponding lower contact 1431 are collaboratively defined as a key intersection. Moreover, the areas of the upper wiring board 141, the spacer layer 142 and the lower wiring board 143 are equal. The plural rubbery elastomers 13 are disposed on the membrane switch circuit member 14. Each rubbery elastomer 13 is aligned with a corresponding key intersection. When the rubbery elastomer 13 is depressed, the rubbery elastomer 13 is subjected to deformation to push the corresponding key intersection of the membrane switch circuit member 14. Consequently, the corresponding key signal is generated.
The plural scissors-type connecting elements 12 are arranged between the base 15 and the plural keycaps 11, and the base 15 and the plural keycaps 11 are connected with each other through the scissors-type connecting elements 12. Each scissors-type connecting element 12 comprises a first frame 121 and a second frame 122. A first end of the first frame 121 is connected with the keycap 11. A second end of the first frame 121 is connected with the base 15. Moreover, the rubbery elastomer 13 is enclosed by the corresponding scissors-type connecting element 12.
The operations of the conventional keyboard device 1 in response to the depressing action of the user will be illustrated as follows. Please refer to FIG. 1 again. When the keycap 11 is depressed by the user, the keycap 11 is moved downwardly to push the corresponding scissors-type connecting element 12 in response to the depressing force. As the keycap 11 is moved downwardly relative to the base 15, the keycap 11 pushes the corresponding rubbery elastomer 13. At the same time, the rubbery elastomer 13 is subjected to deformation to push the membrane switch circuit member 14 and trigger the corresponding key intersection of the membrane switch circuit member 14. Consequently, the membrane switch circuit member 14 generates a corresponding key signal. When the keycap 11 is no longer depressed by the user, no external force is applied to the keycap 11 and the rubbery elastomer 13 is no longer pushed by the keycap 11. In response to the elasticity of the rubbery elastomer 13, the rubbery elastomer 13 is restored to its original shape to provide an upward elastic restoring force. Consequently, the keycap 11 is returned to its original position where it is not depressed.
Recently, the general trends of designing electronic devices and their peripheral devices are toward slimness, light weightiness an easy portability. Consequently, keyboard devices and other peripheral devices need to meet the requirements of slimness. For achieving this purpose, the manufacturers make efforts in minimizing the thickness of the keyboard devices. Under this circumstance, the movable distance of the keycap (also referred as a travelling distance) is shortened. Consequently, the tactile feel of depressing the key of the keyboard device is deteriorated.
Therefore, there is a need of providing a key structure with reduced thickness and enhanced tactile feel.